The present disclosure relates to high-frequency signal amplifier circuits, power amplifier modules, front-end circuits, and communication apparatuses.
Nowadays, a cellular phone is required to support a plurality of frequency bands (multiband use) while the cellular phone being a single terminal. A front-end circuit that supports the multiband use is required to propagate transmission and reception signals corresponding to a plurality of frequency bands without necessarily the transmission and reception signals being deteriorated. As such, a high-frequency signal amplifier circuit for amplifying the transmission signal is required to lower a reception band noise level during a transmission time while maintaining high amplification performance.
International Publication No. WO 2014/087479 discloses a high-frequency power amplifier that aims at suppressing out-of-band noise. FIG. 7 is a circuit block diagram of the high-frequency power amplifier described in International Publication No. WO 2014/087479. The high-frequency power amplifier shown in FIG. 7 includes an RF input terminal 501, an RF output terminal 505, an input matching circuit 502, a high-frequency signal amplifier transistor 503, an output matching circuit 504, a bias circuit 506, and a series resonance circuit 507. One end of the series resonance circuit 507 is connected between the high-frequency signal amplifier transistor 503 and the bias circuit 506 while the other end thereof is grounded, and the series resonance circuit 507 includes an inductor 508 and a capacitor 509. According to this configuration, a situation where noise of a difference frequency band generated in the bias circuit 506 is inputted into the high-frequency signal amplifier transistor 503 can be suppressed, whereby out-of-band noise can be suppressed without necessarily lowering a transmission band gain.